A drummer, as a user of a drum system, beats a plurality of drums holding sticks in both hands and at the same time beats a bass drum by stamping a drum pedal with a foot or both feet during a performance, so that characteristic beating sounds are generated.
Since when the drummer plays the bass drum usually a drum pedal comprising mechanical devices (see for example, Ref.1, Ref.2 and Ref.3) is stamped with foot or feet, it is difficult for the drummer to adjust the beating force against the bass drum.